This invention relates to the field of breathing regulators and, in particular, it relates to multipurpose breathing regulators incorporating a pilot valve to regulate the flow of pressurized gas.
The use of pilot valves to permit small control forces to actuate the opening and closing of a main valve against large pressure gradients is well known. A pilot valve, by definition, meters a small amount of high pressure fluid through one end of a valve spool having an adequate net cross-sectional area to develop the force on the spool required to hold the main valve closed. Venting the pressure behind the spool allows line pressure to unseat the spool, opening the valve.
Presently, breathing regulators which use pilot valves typically utilize large diaphragms and linkages which provide the force and leverage necessary to control the venting of the valve spool control pressure. Nevertheless, the flow rate is quite often severely limited because of instabilities in valve operation known as "flutter" or "chatter". Moreover, the present pilot valve actuated breathing regulators are frequently delicate, large, and complex, requiring fine adjustment and protection from the operating environment.
Another limitation found in present breathing regulators stems from the need to provide balanced inhalation and exhalation pressures. At present, the breathing regulators used in medical applications accomplish this result by using separate inhalation and exhalation valves which must be separately adjusted to achieve the proper balance.
Specifically, therapeutic medical respirators and resuscitators that provide positive pressure breathing all have separate exhalation valves that must be locked shut during pressurized breathing. Separate mechanical or pneumatic actuators are required to accomplish this result. Furthermore, such respirators that provide adjustable automatic (timed) positive pressure breathing frequently require elaborate casing assemblies to contain the basic valve and its controls, and complex hose assemblies leading to the patient's face mask or tracheal tube. Furthermore, at present, only very large and expensive therapeutic respirators offer positive end expiratory pressure (PEEP). Moreover, the PEEP capability of many such machines is only passive, resisting outflow, but not actively maintaining the set pressure.
Although the use of pilot actuated valving mechanisms is known in scuba and contaminated air respiration systems, the valve mechanisms used in such applications require the use of large diaphragms and complex mechanical linkages which make such mechanisms relatively large and which severely limit their reliability. Furthermore, in contaminated air respiration systems, continuous positive pressure to combat leaks in the system has been provided by utilizing a separate exhaust valve actuated by a heavy spring.
The use of pilot actuated valving mechanisms is also well known in high altitude aviation respiration systems. However, at present such systems lack the negative pressure capability for the protection of an aviator's air passages during explosive decompression. Furthermore, such respiration systems typically require forceful exhalation.